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Subject[PATCH v2 19/45] irq: Use get/put_online_cpus_atomic() to prevent CPU offline
Date
Once stop_machine() is gone from the CPU offline path, we won't be able
to depend on disabling preemption to prevent CPUs from going offline
from under us.

Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going
offline, while invoking from atomic context.

Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

kernel/irq/manage.c | 7 +++++++
kernel/irq/proc.c | 3 +++
2 files changed, 10 insertions(+)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index e16caa8..4d89f19 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -18,6 +18,7 @@
#include <linux/sched.h>
#include <linux/sched/rt.h>
#include <linux/task_work.h>
+#include <linux/cpu.h>

#include "internals.h"

@@ -202,9 +203,11 @@ int irq_set_affinity(unsigned int irq, const struct cpumask *mask)
if (!desc)
return -EINVAL;

+ get_online_cpus_atomic();
raw_spin_lock_irqsave(&desc->lock, flags);
ret = __irq_set_affinity_locked(irq_desc_get_irq_data(desc), mask);
raw_spin_unlock_irqrestore(&desc->lock, flags);
+ put_online_cpus_atomic();
return ret;
}

@@ -343,9 +346,11 @@ int irq_select_affinity_usr(unsigned int irq, struct cpumask *mask)
unsigned long flags;
int ret;

+ get_online_cpus_atomic();
raw_spin_lock_irqsave(&desc->lock, flags);
ret = setup_affinity(irq, desc, mask);
raw_spin_unlock_irqrestore(&desc->lock, flags);
+ put_online_cpus_atomic();
return ret;
}

@@ -1128,7 +1133,9 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
}

/* Set default affinity mask once everything is setup */
+ get_online_cpus_atomic();
setup_affinity(irq, desc, mask);
+ put_online_cpus_atomic();

} else if (new->flags & IRQF_TRIGGER_MASK) {
unsigned int nmsk = new->flags & IRQF_TRIGGER_MASK;
diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
index 19ed5c4..47f9a74 100644
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -7,6 +7,7 @@
*/

#include <linux/irq.h>
+#include <linux/cpu.h>
#include <linux/gfp.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
@@ -441,6 +442,7 @@ int show_interrupts(struct seq_file *p, void *v)
if (!desc)
return 0;

+ get_online_cpus_atomic();
raw_spin_lock_irqsave(&desc->lock, flags);
for_each_online_cpu(j)
any_count |= kstat_irqs_cpu(i, j);
@@ -477,6 +479,7 @@ int show_interrupts(struct seq_file *p, void *v)
seq_putc(p, '\n');
out:
raw_spin_unlock_irqrestore(&desc->lock, flags);
+ put_online_cpus_atomic();
return 0;
}
#endif


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